There are many different draft types that fantasy players can use. These include:
A mock draft is not a real draft. Think of it as more of a practice draft for players to get an idea on which players are going where. Players use mock drafts in order to develop strategies for when the real draft happens.
An automated or autopick draft is where the player cannot control the pick. Instead, each pick is automated and takes the best player available as decided by the database beforehand.
A linear or straight draft is a draft that works very similar to how the real NFL draft works. There is a set order that is followed in each round of the draft. So if you pick first in the first round, you will pick first in every other round. In the NFL, when teams are operating with actual people and parity is sought after by the commissioner, having a straight draft makes sense. However, in fantasy, the linear draft is rarely used.
The snake or serpentine draft is the most common draft in fantasy football. The snake draft works by mirroring the first two rounds and continuing from there. For example, in a 10 person draft, the person who picks first will also pick 20th and 21st. The person who picks fifth will pick, 16th, 25th, and so on. This gives players picking at the end of odd rounds a chance to compete as they can get the top players of the even rounds. Because of this fairness, the snake draft is extremely popular.
Auction drafts work very similarly to real life auctions. Each team is given a starting amount of money. As the database rolls through each player, teams offer money with the player going to the highest bidder. There is plenty of strategy as blowing your money early on a few good players would hurt your chances of getting solid contributors later on in the draft. While confusing, auction drafts can be fun particularly for experienced players.
A value based draft is a draft strategy where the fantasy player picks the best player relative to differing factors of value. For example, if a running back is way more valuable than the average back, the fantasy player will pick that player. A fantasy player will not pick based upon average draft position but rather value as compared to the average.